Fossil Insects from the Eocene Florissant Fossil Beds (Teller Co, Colorado)

[Opabinia Blues]

Being a Colorado native, I have taken multiple trips to the public-access Florissant Fossil Quarry located near Florissant Fossil Beds National Monument in Florissant, Teller County, Colorado. This quarry provides fossil collectors fantastic access to the shale layers of the Florissant Formation, a late Eocene (Priabonian, ~34 million years old give or take) lagerstatte known for its diverse fauna of fossil insects, in addition to plants, gastropods, and very rarely vertebrates. Most fossils occur in very thinly laminated ashy grey shales. Other lithologies present include well-sorted tan course sandstones and well-sorted grey claystones. A lacustrine depositional environment is apparent, and though the Florissant Formation has previously been interpreted as the remains of a single large lake (the retroactively named Lake Florissant), it is now generally thought that deposition occurred across several smaller lakes, which of course shifted in their exact location throughout the period of deposition.

 

This thread is for me to share some of my better quality (or more interesting) fossil insect finds from the Florissant Fossil Quarry, and to allow other people to share their Florissant insects. I intend on updating this thread as I make more collecting trips. Most insect fossils found at Florissant are of poor quality, however exceptionally beautiful specimens do crop up quite frequently. Regardless, identification even down to family level is usually very difficult, and some specimens I even have difficulty assigning to an order.

 

Additional reading: https://bioone.org/journals/palaios/volume-27/issue-7/palo.2011.p11-084r/DEPOSITIONAL-SETTING-AND-FOSSIL-INSECT-PRESERVATION--A-STUDY-OF/10.2110/palo.2011.p11-084r.short

 

Please note that at least for now picture quality is not ideal. I do not have the capacity to take good quality macro photographs, but I am doing the best that I can. The scale of the ruler is millimeters, magnification (when applicable) is noted.

 

Order Diptera (True flies):

 

Probably my best-preserved Florissant insect (and one of the first ones I ever found). Another fly. I'd like to be able to identify this one to family (and it almost certainly is identifiable to family) but I haven't been able to place it. This is a gorgeous fossil!

 

Magnified 20X under a stereo microscope. Another gorgeous fossil fly. Possibly a gnat (suborder Nematocera), but I'm not 100% on this identification.

 

Partial fly of indeterminate family, most of the abdomen is apparently missing. Both wings are preserved, the thorax and head are also nicely detailed.

 

This is an example of a march fly (Family Bibionidae), probably the most common insect at Florissant. Many specimens (such as this one) are preserved without their wings. The head and mouthparts are very nicely preserved here, I feel shameful that I could not manage a better photograph.

 

Crane fly, (Family Tipulidae). The preservation quality is not fantastic, but the gross anatomy can be easily made out (both wings, the abdomen, thorax, head, eyes, and even the halteres and some of the legs are present).

 

Order Hymenoptera (Bees, ants, wasps, and relatives):

 

A nice solitary bee (clade Anthophila). The details are not as high-fidelty as some other Florissant insects, but a nice complete specimen.

 

Order Hemiptera (True bugs):

 

Magnified 20X under a stereo microscope. A shield bug (superfamily Pentatamoidea). This is a really neat specimen because fossil Hemipterans aren't particularly common.

 

Indeterminate Order:

 

A large insect that I've never quite been able to place. Two wings are very faintly preserved which would normally be indicitave of a fly, but this specimen just doesn't look much like a fly otherwise. The antennae are interesting, it's a very large insect, and the tibia has an interesting flange. Unfortunately I can't seem to get a good look at the mouthparts (which has been very useful for me in the past for identification).

 

Magnified 20X under a stereo microscope. At first I thought this might be an ant (family Formicidae) but under magnification the shape of the head is more suggestive of a fly. Very poor preservation, I'm not confident I'll ever get a solid answer here.

 

Larvae:

 

A nice plump fly larva, looks to me to be from a botfly (family Oestridae) or a relative.

 

A very strange fossil. The segmentation and tagmosis definitely means this is an arthropod of some sort, and an insect larva is my current interpretation. Still, I've never seen anything quite like it. I've had a few people suggest to me this might be the abdomen of an earwig, but that's definitely not the case (earwig cerci do not look like this or articulate with the abdomen in this manner).

 

Non-Insect Invertebrates:

 

Just an example of one of the tiny gastropods that are common. It takes a keen eye to see them, but once you can recognize them you realize they're very plentiful.

 

If you have some fossil insects from this locality in your collection, feel free to post them here too!

 

Cheers!

Edited October 2, 2022 by Opabinia Blues

[Mikrogeophagus]

Wow never heard of this place before. Some impressive stuff! I think that larva is especially cool. Gotta write that one down for places to go in Colorado.

[RJB]

Nice report with lots of cool pics. One of the places I always wanted to go to but never  made it. 

 

RB

[Top Trilo]

Nice collection! I agree the larva is really cool!

 

I have some insects from Florissant although some may not be as nice as the ones you've shown.

 

Some fly, I assume 5mm long.

 

Likely another fly, this one has a bit more detail on the wing.

 

I'm unsure what this one is, its 5mm and the body and legs are nicely preserved.

 

This small one is 4mm and not the best preservation but has nice eyes.

 

These images I had readily available from my trip report in May, I'll see if I have any other ones worth posting.

 

[Packy]

you can order bags of material from them. 

[Crusty_Crab]

I actually returned a couple weeks ago from a trip there. I've been slowly processing my finds, but here are the best ones:

 

A weevil, family Curculionidae. I believe Scudder had described many species of weevils from Florissant so patient study may narrow this down some more. 

 

 Another weevil to my eyes

 

A leafhopper?

 

A crane fly on the left and winged ant on the right. I like this one because you can see the veins of the wing clearly

 

[Nimravis]

4 minutes ago, Crusty_Crab said:

actually returned a couple weeks ago from a trip there. I've been slowly processing my finds, but here are the best ones:

Nice finds- Congrats 

[Opabinia Blues]

1 hour ago, Crusty_Crab said:

I actually returned a couple weeks ago from a trip there. I've been slowly processing my finds, but here are the best ones:

 

A weevil, family Curculionidae. I believe Scudder had described many species of weevils from Florissant so patient study may narrow this down some more. 

 

 Another weevil to my eyes

 

A leafhopper?

 

A crane fly on the left and winged ant on the right. I like this one because you can see the veins of the wing clearly

 

Those weevils are fantastic! Also, I agree with your leafhopper ID. Looks like a very productive trip.

[Crusty_Crab]

22 hours ago, Opabinia Blues said:

Those weevils are fantastic! Also, I agree with your leafhopper ID. Looks like a very productive trip.

Thanks for the confirmation on the ID! 

 

I was there last year as well and below are a selection of finds:

 

A thrip, order Thysanoptera. This might be undescribed since Scudder didn't describe any thrips and I'm not sure there have been any described from Florissant since.

 

Another winged ant:

 

A beetle, my best guess is a soldier beetle (family Cantharidae)?:

 

 

 

 

[Thrips-iD]

Hi Crusty_Crab,

where is this thrips (Thysanoptera) located please? Is it in a private collection? If so, is it for sale?

Thanks Manfred.

 

www.thrips-iD.com

[erose]

Many many moons ago I visited Creede, CO. And went home with lots of plants. A very similar caldera ash depsit. Bugs are known but not as. common as Florissant. Your insects are very cool.